1. Field of the Invention
The invention relates to vacuum coffee makers.
2. Description of Prior Art
In a vacuum coffee maker, there are two containers one above the other with a tube extending down from the bottom of the upper container through the lower container to adjacent its base. Conventionally the lower container has a base integrally formed with the rest of the container which is arranged to be heated by a flaming burner or grill plate. A filter is placed at the top of the tube, that is in the bottom of the upper container, and dry coffee grounds placed on top of the filter. The lower container is filled with water, usually pre-heated, and the two containers fitted together and separated and sealed by a supporting resilient stopper.
In order to prepare coffee, a burner is placed under the base of the lower container to heat the water. As the water expands and boils, water is forced up the tube past the filter and into the upper container, mixing with the coffee. When the water has all evaporated in the lower container, the burner is removed. Water is drawn down through the filter by vacuum to the lower container, the upper container is removed and the freshly made coffee served from the lower container.
Such vacuum coffee makers however require supervision, particularly to remove the burner at the required time. Also, the flow of water up the tube, especially when only a small quantity remains in the lower container, can become erratic due formation of steam bubbles from the heater surface. This leads to spasmodic flow of water upwards through the tube especially towards the end of a heating cycle.